It's a controversial topic. I am currently on Xarelto, ( a prescription blood thinner ), so I have to be wary of supplements that might cause additional thinning . Some say CoQ10 does, there's not evidence of it that I've seen. I still take 200 mg of ubiquinol. Fish oil and vitamin E can definitely thin blood in high enough doses. I limit my fish oil and vitamin E, ..2000 mg fish oil, 400 iu tocotrienols, and gamma E.

I'm not sure why it would be controversial. There's an objective measure of blood clotting ability, known as the Prothrombin Time. This could be measured before and after people are dosed with any supplement, and compared. Maybe the controversy comes in because the measurements haven't been done, so we're stuck with people's claims. I don't know. At any rate, Fish Oil and Vitamin E are known problems. Warfarin is a blood thinner that works by causing a Vitamin K deficiency. Supplemental Vitamin K is antagonistic, but it just normalizes clotting; that doesn't mean that extra vitamin K would "thicken" the blood, or cause excess clotting in someone who didn't take Warfarin, absent some weird genetic defect.

I think that most supplements don't have much of an effect on clotting.

The controversy exists because so little is really known about the blood thinning potential of many of the supplements we take, and there are contradictory claims. CoQ10 is a classic example, so is curcumin. . The problem with Coumadin and the PT/ INR tests is that they are so erratic.
The new class of blood thinners like Xerelto can't be reversed with vitamin K like warfarin can. So ingesting other potential anticoagulants or blood thinners can be hazardous .

Vitamin K regulates blood coagulation . It isn't a blood " thickener " per se. It is an antidote for blood thinners like warfarin. It ISN'T a blood thinner. " Things " that bring down cholesterol , like statins? Statin therapy isn't contraindicated for people on warfarin...

Sounds like we might have multiple definitions for "blood thinner", which doesn't surprise me, since it's a pretty vague term. Are we talking about prothrombin time, or the apparent "viscosity" of blood, or "gee, my blood feels thinner today"? There are other objective measures besides prothrombin time- I'd rather see the data than just hear claims, but it's probably the case that the data doesn't exist on many supplements.

Practically only the addition of one agent increased bleeding: blood in stool, blood in mucous of the nose, and much more liquid blood (taking glucose readings) - and that's 1 innocent 81mg baby aspirin.

I've taken many blood thinning supplements over the years, yet I've never had a problem with bruising, bleeding (gums etc) and even my shaving nicks stop promptly.

My girlfriend on the other hand takes almost no supplements at all, but she does take moderate amounts of aspirin for her headaches. She bruises horribly with the slightest bump and says her shaving nicks hemorrhage for 5 to 10 minutes and she must hold pressure with a tissue on them to make them stop.

Surgical procedures aside, I thing the whole bleeding promoting supplements kerfuffle is substantially overblown. Plavix and other prescription thinners are now prescribed so frequently it seems like everyone will be on them eventually if you live long enough. If the big guns thinners are so safe and good for so many people, I should think the minor thinning effect of most supplements in this category might also be considered as helpful more often than not so long as you are not at substantial risk for a serious GI bleed.

I've noticed anti-supplement propaganda has increased sharply over the last year or so and the bleeding risk is one of the favorite talking points. I'm a 57 year old male and I could use some moderate thinning so I'm not sweating my vitamin-E a bit. It may just save my life! Concern over mixing them with prescription thinners may be a valid point but I just say NO to prescription meds.

I take 100+ supplements and I definitely have increased bleeding time. I don't have any extreme symptoms like petechiae. I suppose it may help me avoid heart disease, although I just hope I don't get in a car accident! My personal theory is that the high incidence of clotting issues and heart disease in modern culture might be caused by not eating "wild plants" (i.e., herbs), most of which seem to prolong bleeding time. Domestic vegetables have had bitter-tasting compounds (alkaloids) bred out of them. If our bodies evolved in times when people ate large quantities of wild plants, then not eating them will cause an unnatural prothrombosis state. My theory, anyway...

Garlic (Allium sativum) - Garlic inhibits platelet aggregation in vivo in a dose-dependent fashion. The effect of one of its constituents, ajoene, appears to be irreversible and may potentiate the effect of other platelet inhibitors such as prostacyclin, forskolin, indomethacin, and dipyridamole.

Ginger (Zingiber officinale) - In an in vitro study, gingerols and related analogues inhibited arachidonic acid-induced human platelet serotonin release and aggregation, with a potency similar to that of aspirin.

Ginseng (Panax ginseng, Panax quinquefolius) - There is concern about ginseng’s effect on hemostasis. One early study suggested that the antiplatelet activity of panaxynol, a constituent of ginseng, may be irreversible in humans. Other studies found that ginseng extract and ginsenosides inhibit platelet aggregation in vitro, and prolong both thrombin time and activated partial thromboplastin time in in vivo animal models.

Green Tea (Camellia sinensis) - In an early in vitro and in vivo study, both green tea and EGCG significantly prolonged mouse tail bleeding time in conscious mice. They inhibited adenosine diphosphate- and collagen-induced rat platelet aggregation in a dose-dependent manner.

Kava (Piper methysticum) - In an in vitro investigation, a kava compound (+)-kavain suppressed the aggregation of human platelets. A pilot survey of extensive usage of kava showed that kava users were more likely to complain of poor health and had increased red-cell volume and decreased platelet volume.

Saw palmetto (Serenoa repens) - Platelet function was not affected by the administration of saw palmetto in a clinical study, and two case reports provided little evidence to implicate saw palmetto as a cause of bleeding. In a patient undergoing a craniotomy, however, saw palmetto was associated with excessive surgical bleeding that required termination of the procedure. This complication was attributed to saw palmetto’s anti-inflammatory effects, specifically the inhibition of cyclooxygenase and subsequent platelet dysfunction.

St John’s Wort (Hypericum perforatum) - The anticoagulant effect of warfarin, a substrate of the 2C9 isoform, was reduced in seven reported cases.

Boldo (Peumus boldus)

Danshen (Salvia miltiorrhiza)

Dong quai (Angelica sinensis)

Papaya (Carica papaya)

Coenzyme Q10 (CoQ10) - Treatment with CoQ10 did not affect the absorption and distribution of the S- and R-enantiomers of warfarin but increased total serum clearance of both R- and S-warfarin.

Glucosamine and Chondroitin Sulfate - In a published report from the FDA MedWatch database, there were 20 reports of glucosamine or glucosamine-chondroitin sulfate use with warfarin. Coagulation was altered as manifested by increased INR or increased bleeding or bruising.

Fish Oil (EPA and DHA) - In vivo studies show that omega-3 fatty acids decreased platelet aggregation but did not influence bleeding time. In a clinical study, the inhibition of platelet aggregation by omega-3 fatty acid was gender-specific. EPA was significantly effective in reducing platelet aggregation in males, whereas DHA was not effective compared to the placebo. In females, DHA significantly reduced platelet aggregation but EPA did not.

Vitamin C

Vitamin E - Vitamin E intakes are associated with an increased tendency to bleed and in vitro and in vivo studies showed that vitamin E inhibits platelet aggregation. A vitamin E quinone metabolite may be responsible for the effects of vitamin E, and the reduced platelet adhesiveness of vitamin E probably accompanies incorporation by plasma lipoproteins

Vitamin K

Commonly Used Dietary Supplements on Coagulation Function during Surgery